Shanaze Reade's desperately courageous exit from the BMX final after three pile-ups remains one of the most dramatic British moments of the Beijing Olympics, and a crash did for her here in Birmingham as well. Exiting early from the BMX world championships was precisely the opposite of what she wanted in the run-in to the London Games, but having breezed faultlessly through her three qualifying runs the Crewe racer came a cropper on the first corner in the quarter-final, and that was that.

This was the first knockout stage of the competition, with the first four to go through, so there was no way back. She crossed the line to sympathetic applause, but it could have been so much more. Her early exit, and that of her male team-mate Liam Phillips with a broken collarbone, will not affect Great Britain's chances of qualifying for the Olympic Games, as the host nation is entitled to one men and one women's slot. Those who believed that her gold in Beijing was virtually a foregone conclusion due to her dominance in the run-up had ignored the completely random element in this discipline. The same caveat should apply as the London 2012 approaches. It would be foolish not to list her among the favourites, but equally foolish to ignore the fact that BMX has a lottery side to it which makes the elimination race on the velodrome, widely dismissed as a demolition derby, look positively sane.

This is cycling, but not as traditionalists know it and the same rules do not apply. The combination of close-quarters mass-start racing with one jump after another taken at speed requiring perfect bike-handling means that crashes are inevitable. It is a great spectacle, calling for a unique combination of skill, courage and speed, but there is a grisly element to it all the same.

Reade's fault here seemed to be the fact that she was simply trying too hard. She came down the start ramp in the pack, was clear of an early faller and then took a small lead over the first jump. She was ahead by several bike lengths, and appeared to be taking control as she hit the first right-hand banked turn. Here she lost adhesion in one or both tyres and could not regain control, coming down on her right side. She was quickly back up, but by then the race was well away from her.

"The speed was that high and [with] the angle of the tyre, the traction just wasn't there," said the Great Britain BMX coach Grant White. "She was going bloody fast into the first corner, tried to take a nice tight line and just slipped out. It's our sport and these things happen."

Whereas before Beijing, Reade seemed unbeatable, having taken straight world titles from 2006-8, she has not had the same aura since, winning just one full world championship, in 2010, and the time-trial title in 2011.

It was obvious that she was not the only one pushing it to the limit. There is no other way to win in this sport. There seemed to be a crash in pretty much every other heat, running the full gamut from four-rider pile-ups through spectacular face plants to pure comedy, such as when a Frenchman piled into a television gantry a yard before the finish. On occasion, the fallers showboated to the finish to warm applause; on others they were helped painfully away.

Reade has already had two heavy crashes in the last three months, damaging her hip and shoulder in the first. In the second, a training crash last week, she knocked herself unconscious and woke up in hospital. During her career, she has broken a knee, a foot, ribs, an elbow, her coccyx and a hand. The damage on Saturday was grazes and bruises.

Reade and Phillips had got the championships off to a flying start on Friday with a silver medal apiece in the time trial, which is a way of whittling down the initial entry and setting the seeding for the massed-start racing, but that was as good as it got. Phillips, having taken the best result of his career, left the championships early after crashing out on the first corner of his qualifying round. He looked to have lost control of his front wheel, and fell heavily on his shoulder, and was taken to hospital for assessment. There was no initial word on how the crash would affect his chances of competing in London.